1. Field of the Invention
This invention relates to a device for protecting the cusps of prosthetic heart valves from interference by suture looping during the implantation or attachment of the valve to the heart tissue of the patient.
2. Description of the Prior Art
Heart valve prostheses are of two general types, mechanical valve protheses and natural tissue prostheses. Natural tissue prostheses are generally considered to be preferable with respect to similarity to natural flow characteristics, minimal thrombogenicity and low incidence of catastrophic in vivo dysfunction.
Pericardial tissue valves and heart valves taken from pigs, suitably processed, are used for implantation in human patients as prosthetic heart valves. These heart valves have plural cusps which are normally in contact with each other at the free ends of the cusps to maintain the valve in normally closed position. However, the cusps are flexible and are forced apart from each other at their free ends, temporarily, by blood pressure engendered by each heartbeat. Illustrative of such prosthetic heart valves are those shown in U.S. Pat. No. 4,477,930 to Totten, et al
Natural tissue heart valves usually have a cloth or fabric covered framework, known as a stent, which incorporates a suture ring at its base so as to facilitate its implantation into the annulus or wall of the heart, using conventional surgical procedures.
When the heart valve is positioned in the mitral valve annulus for surgical implantation by suturing its suture ring to the annulus, the valve cusps face away from the surgeon, and the space beyond the valve cusps (within the heart cavity) is hidden from the view of the surgeon. It is therefore possible that a suture loop formed during the suturing procedure may extend beyond the free ends of the cusps and may become entangled in one or more of the cusps when the loop is reduced in size as the suture needle is pulled to tighten the stitch. Such entanglement interferes with the intended operation of the valve and may result in damage to the valve cusps, thereby making the valve unsuitable for its purpose.
This invention provides a device for the protection of a natural tissue heart valve, synthetic leaflet heart valves, or the like, from interference or damage by suture looping.